Furnace



United States Patent 2,925,260 FURNACE -Richard C. Dickey, Streator,rlll., assignor to iFerro Corporation, Cleveland, (Zlhio, a corporation of Ohio Application May 2s, lasaserial No. 587,524

.s claims. (ci. zas-fs) invention relates as 'indicated to furnace construction andhas; more 'particular reference to lcertain improvements :in furnaces of the type commonly usedini'ring :porcelain enamel'on metal orin numerousother heating 'operations where {ware "is Iconveyed through va furnace in vmore or ll'ess 'continuous manner. v v

Although the `furnace'iillustrated andjdescribed :herein is particularly .adapted for porcelain enamelling, it will be understoo'dby those skilled `in theart'th'at the features disclosed 'herein are readily adaptable to furnaces intended for annealling or otherheat treating operations. Further, while the present specification',k describes the present invention rbeing utilized `in a U-type muie furnace it is to be understood that the `present invention is also applicable in straight-through furnaces a'nd furnaces rvwhether U`-type 'A very 'eiiicientY and successful form -of'continuous furnace isi'the 'so-*called 'U-type in which the'furnace struc- 'ture is open at `one endand closed at the other end and vmeans areprovided fortransporting ware into and out of ythe furnace Vin ya U-shaped path. In this form of furnace 'the heating zoneis 'disposed at the closed end of the U, and the coldincoming `ware enters the open end ofthe furnace rand movesclose to,`but.in the opposite direction from the heated outgoingware.V Thus the entering wareis ,preheated by the heat given oifby the outgoing Ware.

It is an object of the present invention Ato provide a furnace whetherk it "is fuel fired, electrically heated or heated `by radiant tubes, which furnace can be heated by convection currents and radiant heat simultaneously. Such 'a furnace will have `far superior heatl distribution enabling the tiring of .ware withV a of Warpa'ge and uniform heat distribution. t

Y Another object of the present linvention includes the provision of 'converting an alreadyexisting radiant Atype furnacejinto `a combination convection 'current-radiant typerlre'ated'furnace whereby such vfurnacecan be used y either asara'diant type furnace or 'a combination of both methods of heating. r Y Other objects ofthe invention will appear'as the de- .,scription, proceeds.

Tofthe accomplishment of the foregoingand related jends,the said invention vthen 'comprises the features hereinaft'erfully described and particularly pointed out in the claims, the 'following ydescription and annexed drawings setting .forth in detail certain illustrative embodiments'of the invention, these being indicative,l however, of but a few of the various ways in "which the principle of the invention may be employed.

In said annexed drawings: Fig. 1 is top plan view of a muiile U-type furnace incorporatingthe present invention;

Fig. 2 is a longitudinal section through the length of one leg of the U of said furnace; t

Fig. 3 isacross sectional View taken' through 3-3 of Fig.1;and M f Fig. 4 is an enlargedview ofthe /air discharge nozzle used in the present invention. v k

Referring more particularly tothe drawings Fig. 1 il- 'lustratesa mule U-type furnace. However, I do'not wish to limit'my inventioneither to a mutlle'furnace Aor to a or straight-through that Yare either :electrically heated or fuel fired.

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2 U-type furnace as `various featuresof the improved construction are readily adaptable to other furnace fdesigns. The furnace illustrated in Fig. 1 comprises a preheat zone ,general indicated atf1,fa hot zone generally indicated at 2 land a cooling zone generally indicated at 3. The radiant yheat `type furnace kin the embodiment illustrated'may -be tired by means of. gas or Vfuel oil burner vjets, or the like, generally and diagrammatically illustrated at'4 '(Fi'g. y17.), which coact with the chambers 14a in the base ofthe furnace to supply heat to the muffle structure M in 'the furnace, and thence by radiation to the ware being heated. in amanner well known to those skilled in the 4muiile-type furnace art. Invother words the work or wareiwhich Iis ybeing heated orfired; is` separated from direct contact with the hot gases at the heating elements, ywith'the -heat being transmitted by conduction through themuflle portions, as for instance 4b, of the furnace, and then by radiation to theware-being heated. The roof'of the f carry Vthe ware `are preferably mounted on van endless chain which goes in the rdirection of the arrow in Fig.v 1. Ware is .loaded on to the conveyor at the openend 17'of the furnace and vmovesinto the .preheating zione generally yindicated at 1 and then into the hot zone generally -indicated at 2 and then passes on out in closely spaced relation yt'o-the incoming Ware through'the cooling, zone generally indicated at 3. Adjacent the underside of the roof there is an alloyk steel duct 7 which starts approximately adjacent the open end ofthe furnace and extends throughoutthe length of the furnace whereat one end 6 of the center lmuiie wall it splits into two legs 8 and 9 and which lterminate at the closed end 4 of the furnace.

The type of alloy steel used 'in lduct 7 is dependent upon the temperatures used in the furnace. Thus the duc't used in an enamelling furnace would have to be made from alloy steel that would withstand the temperatures used in -iring porcelain enamel (about 14001600 F.).

As thered ware emerges from the discharge vend of the furnace 'through opening `10 the `air `in that general area is heatedto approximately 500 F. bythe heat dissipated .from the red ware. This warmed air -is picked up by a high pressure blower 11 and blown into alloy "tube 7 and as 'the heated air progresses through alloy tube 7 it keeps getting hotter as it approaches the hot zone 2 ofthe furnace. Finally when the air reaches the'legs 8 Aand lwhich are disposed on each side of the center muifle 5 the `air at this approximate area reaches the ambient temperature of the'mule. As the air is being pushed through alloy tubes7 by high pressure blower 11 it is simultaneously also being discharged into the preheat and heating zone through discharge `tubes 12 and out through high pressure nozzles `13. It will be noted that there are a multiplicity of discharge'tubesv 12 dependingdownwardlyfrom alloy tube 7 and terminating at various levels between the duct 7 and the oor of the furnace. The number of the downwardly depending discharge tubes 12 are dependent upon the overall sizeof the furnace., It will also be noted that the discharge nozzles 13 are disposed at various levels throughout the furnace. This is done so that there is an even distribution of moving hot air at all levels from the top tol bottoml of the furnace. Thus ware being tired through the furnacewill be hit by hot air atv the top of the piece, the middle of the piece and the bottom of the piece evenly thus causing even tiring of the piece.

' 2,925,260 l Patented Feb.- l16,1960

Referring specifically to Fig. 4 it will be seen that the discharge nozzle 13 is what is known as a high pressure type. The discharge nozzle 13 is tapered as at 14 and is inserted into a larger orifice 15 thus giving a Venturi effect which sucks the heated air of the furnace through the larger discharge portion 1S thus causing convection currents in the furnace.

From the foregoing description and drawings it can now be readily seen that I have provided a suitable means for-converting an existing radiant type furnace into a type which combines the benefits of convection heating and radiant heating. It will also been seen that at any time the operator can turn oif the high pressure blower 11 and thus very simply convert the furnace back to a straight radiant typeof furnace. It will also be readily recognized that this system can be used to convert existing furnaces and can also be built into new furnaces thus resulting in a combination convection and radiant heat furnace.

Other modes of applying the principle of the invention may be employed, change being made as regard the details described, provided the features stated in any of the following claims or the equivalent of such be employed.

I, therefore, particularly point out and distinctly claim as my invention:

l. In an elongated, U-type, center wall mule furnace for porcelain enamelling and the like, said furnace comprising side walls, a top wall and an end wall defining a furnace enclosure in the interior of which Work may be moved sequentially along a U-shaped path, said furnace having an open work receiving and work discharging end and a closed end defined by said end wall, said furnace including muiiie structure disposed intermediate said side walls through which the work is adapted to pass, said mufe structure including a bottom wall extending intermediate said furnace side walls, heating chambers in said furnace disposed beneath said muffle structure bottom wall for transferring heat through said bottom wall solely by conduction from whence it is transferred by radiation to the worksaid muiiie structure operating to separate the work from direct contact with hot gases of combustion in said chambers, a center muflie wall of said furnace projecting upwardly from said bottom wall and terminating short of said furnace top wall, said center muflie wall commencing generally adjacent to but in spaced relation to said end Wall and extending lengthwise toward said open end of said furnace, the combination therewith of a main heating air distributing duct extending longitudinally interiorly of the furnace substantially from u said open end to said closed end and being directly exposed to the heating influence in said furnace,4 said duct being bifuroated adjacent said last mentioned end to dene a pair of leg portions disposed on opposite sides of said center wall interiorly of said mufe structure, means for withdrawing heated air from said furnace enclosure and introducing the same into said duct under superatinospheric pressure, a plurality of longitudinally spaced branch discharge ducts depending from said main duct along substantially its full length, each of said branch ducts having a single latertally directed orice therein at the lowermost end thereof for discharging heated air into the furnace interior, said orifices in adjacent branch ducts and in a direction longitudinally of said furnace being disposed at different elevations With respect to one another and said orifices in said branch ducts which are connected to said leg portions discharging air in a direction toward the respective of said furnace side walls and across said muiiie structure bottom Wall, whereby heated air is discharged in vertically staggered fashion into the furnace interior to create a condition of turbulence therein and thus provide a heating environment wherein work will be uniformly and efficiently heated by a combination of convection currents and radiant heat.

2. In an elongated, U-type, center wall muffle furnace in accordance with claim 1 wherein the interior surface 75 of each of said orifices at the outer terminal end thereof is convergent in an outward direction, a generally tubular-like member open at both ends receiving said terminal end in encircling relation, said tubular-like mem ber defining a larger orifice having an interior surface which is convergent in the same direction as the iirst mentioned interior surface.

3. In an elongated, U-type, center wall mufiie furnace for porcelain enamelling and the like, said furnace comprising side walls, a top wall vand an end wall defining a furnace enclosure in the interior of which work may be moved sequentially along a U-shaped path, said furnace having an open work receiving and work discharging end and a closed end deiined by said end wall, said furnace including pre-heating, firing and cooling zones disposed in that order along the U-shaped path of movement of the work, said furnace including muiiie structure disposed intermediate said side walls and in said tiring zone through which the work is adapted to pass, said muflie structure including a bottom wall extending intermediate said furnace side walls, heating chambers in said furnace disposed beneath said muie structure bottom wall'for transferring heat through said bottom wall solely by conduction from whence it is transferred by radiation to the work, said mulile structure operating to separate the work from direct contact with hot gases of combustion in said chambers, a center muie Wall of sald furnace projecting upwardly from said bottom wall and terminating short of said furnace top wall, said center munie. wall commencing generally adjacent to but in spaced relation to said end wall and extending lengthwise toward said open end of said furnace to partially divide said muie structure into two laterally spaced sections, the combination therewith of a main heating air distributing duct extending longitudinally interiorly of the furnace substantially from said open end to said closed end and being directly exposed to the heating inuence in said furnace, said duct being bifurcated adjacent said last mentioned end to define a pair of leg portions disposed on opposite sides of said center wall interiorly of said mufe structure, a high pressure blower mounted exteriorly of said furnace enclosure and communicating with the furnace interior and with said duct in the neighborhood of said open end to introduce heated air from said furnace into said duct and under super-atmospheric pressure, a plurality of longitudinally spaced branch discharge ducts depending from said main duct along substantially its full length, cach Yof said branch ducts having a single laterally directed orifice therein at the lowermost end thereof for discharging heated air into the furnace interior, said orifices in adjacent branch ducts and in a direction longitudinally of said .furnace being disposed at different elevations with respect ,to one another, and said` orifices in sald 'branch ducts which are connected to said leg portions being dis` `posed at different elevations with respect toone another in a direction transverse of said furnace enclosure, said last mentioned orifices discharging heated air in a dir'ection toward the respective of said furnace side walls and across said inuiiie structure bottom wall, whereby heated air is discharged in vertically staggered fashion into the furnace interior to create a condition of turbulence therein and thus provide a heating environment wherein work will be uniformly and eciently heated by a combination of convection currents and radiant heat.

References Cited in the iile of'this patent UNITED STATES PATENTS A1,717,115 McCann June 11, 1929 2,230,800 Hormel Feb. 4, 1941 2,385,962 Barnett Oct. 2, `1945 FOREIGN PATENTS p 27,839 Great Britain Q 1904 92,875 Switzerland Apr. 1, 1922 

